JPS63257445A - 3-phase brushless motor - Google Patents

Abstract

PURPOSE:To restrain torque ripple, by providing respective main magnetic poles with 5 pieces of auxiliary magnetic poles respectively. CONSTITUTION:Coils 2 are arranged in a magnetic circuit, consisting of a mag net 1, a rotor yoke 3 and a stator yoke 4 and a torque is generated by the current of the coils 2 and the intersecting flux of the magnetic circuit, while 3-phase coils 2A, 2B, 2C repeat the conduction of electric angle 120 deg. and the non-conduction of electric angle 60 deg. respectively and alternately. ' The resultant torque of the 3-phase torque waveforms 7a, 8a, 9a becomes a torque 10a and a torque ripple, 14% of the resultant torque, is generated. On the other hand, the torque waveforms 7b, 8b, 9b of an auxiliary magnetic pole 1B become 1/5 of the period of the sine wave of a torque generated by the main magnetic pole. The torque of respective coils 2A, 2B, 2C becomes the resultant of both magnetic poles 1A, 1B and the waveforms thereof become the waveforms 7c, 8c, 9c. Accordingly, the resultant torque of 3 phases phi1-phi3 is provided with the waveform 10b and the waveform of torque, reduced in the ripple and flat as compared with the waveform 10a of the torque of the main magnetic pole 1A, may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a three-phase brushless motor, and more particularly to a small-sized brushless motor with improved torque ripple.

[Prior Art] Three-phase brushless motors are used as capstan motors for 8 mm VTRs and the like. In this type of low-speed, small-sized motor with small inertia, torque ripple is likely to occur, and reducing the ripple is an important issue.

As a method for reducing torque ripple during motor rotation, Japanese Patent Laid-Open No. 57-208267 and Japanese Patent Laid-Open No. 58-22
As seen in Publication No. 574, one or two non-magnetized parts or magnetized parts of opposite polarity are provided in a part of the multipoles of a multi-pole magnet, and the torque waveform generated in the coil is controlled. A method of suppressing the ripple component of the torque of one coil or the composite torque of a plurality of coils is known.

FIG. 1θ and FIG. 11 show a conventional three-phase bidirectional 12o.

FIG. 3 is a diagram showing an example of a magnetic pole structure of a magnet in a current-carrying brushless motor. In Fig. 1O, inside each main pole M of the multipole magnet, there are two parts opposite to the main pole at two positions approximately 1/3 of the multipole opening angle (60° and 120" in electrical angle). Polarized or non-magnetized commutators m1 and m2 are provided. In FIG. 11, commutative poles m3 and m4 are the first
It is provided at the same electrical angle position as the commutating poles m1 and m2 in Figure 0, occupying the entire length in the radial direction.

[Problems to be Solved by the Invention] This German motor is particularly required to be small, thin, lightweight, and high torque, so the winding width of the coil is designed to be relatively large. However, in a motor designed with a large coil winding width, the main pole opening angle is 173 and the electrical angle is 60'.
'' and 120°, the method of providing a non-magnetized or a commutating pole with a polarity opposite to that of the main pole can only provide a commutating pole with a very small width in the electrical angle direction. It has to be smaller than the coil winding width.

Therefore, in such a design, the correction torque generated by the interpolation generated in each ring wire and each tree forming the coil has a phase shift of the electric current corresponding to the width of the coil winding, and this is large, so The correction torque generated by one combined coil cannot be obtained efficiently. Another drawback is that it becomes difficult to maintain the necessary torque.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a brushless motor that is small in size, has little torque ripple, and can obtain sufficient torque.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a three-phase brushless motor having a multi-pole magnetized magnet and a plurality of air-core coils facing the magnet. , the magnet has an even number of main magnetic poles, and each main magnetic pole has a sub-magnetic pole part on the outermost part of the surface facing the coil, and the sub-pole part is approximately divided into five parts of the outermost part of each main magnetic pole. It consists of five sub-poles of the same shape, the opening angle of the coil is approximately equal to the opening angle of each main pole of the magnet, and the winding width of the coil is approximately equal to the circumferential width of each sub-pole.

[Function] In the present invention, the magnet has a plurality of main magnetic poles,
Each main pole has a sub-pole section consisting of five correction sub-poles on the outer periphery, and the winding opening angle of the coil facing the magnet is approximately equal to the magnet main pole opening angle, and the coil winding width is By making the width approximately equal to the width of the sub magnetic pole, a fifth harmonic torque waveform of the main magnetic pole torque waveform obtained at the sub magnetic pole can be efficiently obtained, and by combining it with the torque waveform obtained at the main magnetic pole, a pseudo-triangular wave torque waveform is created. is obtained to smooth the composite torque with the coils of other phases. By efficiently obtaining the fifth-order harmonic torque component obtained from the sub-magnetic pole, the radial width of the sub-magnetic pole can be minimized, and as a result, the main pole area is hardly reduced and the generated torque is almost sacrificed. This makes it possible to reduce torque ripple without causing any problems, and makes it possible to achieve both of these contradictory characteristics.

[Example] The present invention will be described in detail below with reference to the drawings.

FIGS. 1 and 2 show magnets and coils with correction magnetic poles when the brushless motor of the present invention is configured with 8 poles and 6 coils. As shown in FIG. 1, the magnet 1 has eight main magnetic poles in this case, and each main magnetic pole 18 is provided with five correction sub-poles IB on its outer periphery. In FIG. 2, 2 represents six air-core coils, each of which is fixed to a yoke 4. In FIG. Details of each magnetic pole and each coil will be explained in detail later.

FIG. 3 is a sectional view of a magnet rotation type brushless motor constructed using the magnet and coil shown above. A rotor yoke 3 to which a magnet 1 is fixed is fixed to a rotor shaft 5, and together constitute a rotor. On the other hand, an air-core coil 2 and a bearing 6 are fixed to the stator yoke 4 to constitute a stator. Bearing 6
rotatably supports the rotor l1h5.

FIG. 4 shows a part of the magnetization pattern of the magnet 10. Five correction sub-poles IB are provided on the outer periphery of the main magnetic pole portion IA that is magnetized in the thickness direction. If the opening angle for one pole of the main magnetic pole IA is α, the opening angle for one pole of the sub magnetic pole 1B is approximately α
15, N poles and S poles are alternately magnetized at approximately equal intervals. The polarity of the central sub-magnetic pole among the five sub-magnetic poles is magnetized to be the same as the polarity of each main magnetic pole. The size of the sub magnetic pole must be such that it produces sufficient correction torque in the coil 2 to correct the torque ripple and does not unnecessarily reduce the torque due to the main 6B pole. For this reason, when the radial width of the main magnetic pole IA is W, the radial width of the sub magnetic pole 1B is preferably 1/3 or less of W.

FIG. 5 shows the shape of the coil 2. The opening angle α of the coil 2 is approximately equal to the opening angle α of one pole of the main magnetic pole IA of the magnet 1. Further, the winding width w3 of the coil 2 is approximately equal to or smaller than the width of one sub-pole IB of the magnet 1. By configuring the coil 2 in this manner, it is possible to efficiently obtain the correction torque by the auxiliary magnetic pole.

Next, the operation will be explained.

As shown in Figure 3, magnet 1 and rotor yoke 3
．． A magnetic circuit is formed by the stator yoke 4, a coil 2 is disposed in the air gap, and torque is generated by the current flowing through the coil 2 and the magnetic flux of the magnetic circuit.

FIG. 6 is a diagram for explaining the operation, and the positional relationship between the magnet 1 and the coil 2 is shown in a developed view for easy understanding. As shown in FIG. 6 (A), the coil 2 is 3. Three phase coils 2A (φ1), 2B (φ2), 2G (φ
3). (B) is the composite torque waveform, (C
) to (E) show the state of the waveform of torque T generated by energizing each coil. This diagram is 3
This is an example of a bidirectional drive brushless motor with 120° phase current, and as shown in the figure, the 3-phase coils 2A (φ1) and 2B (
φ2) and 2G (φ3) are energized at 120° in electrical angle and energized at 60° based on the phase relationship of 120° in electrical angle.
No electricity in ten directions.

Repeat alternately in one direction.

Now, the torque waveforms generated only to the main magnetic pole 1 are 7a for φ1, 8a for φ2, and 9a for φ3, which are shown by dotted lines, and form a part of a habosine waveform. In addition, the combined torque of the three phases is 10a shown by the dotted line in the same figure (B),
This also almost has the shape of a part of a sine waveform. The ripple of this composite torque is the peak-to-peak value TP-
P (x), it is expressed as Tmax-T+alr+"-")=(T@az+T@In)/2xl", so if the torque waveform is a sine wave, the peak
It produces a torque ripple of about 14% at the peak value.

On the other hand, the torque waveform generated only by the sub magnetic pole IB is 7b for φ1, 8b1 for φ2, and 9b for φ3 as shown by the dotted line, and these also have an almost sine wave shape, and are 175 ( 5th harmonic), which has a period of 72 degrees in electrical angle.

The torque generated in each of the coils 2A (φ1), 2B (φ2), and 2G (φ3) is a combination of the torque generated by the main magnetic pole IA and the sub magnetic pole 1B, so φl is 7c1 and φ2 is 8c, as shown by the solid line. , φ3 is 9C and almost triangular torque,
This results in a waveform.

3 phase φ1. φ2. The resultant torque of φ3 is as shown in the torque waveform 10b shown by the solid line in FIG. 6(B), and the main magnetic pole I
Only in A can be obtained a torque waveform with a flattened head and fewer ripples than the torque waveform 10a.

The ripple amount at this time is determined by the amplitude of the fifth-order harmonic torques 7b, 8b, and 9b generated at the sub magnetic pole IB. The factor of the amplitude is the winding width W3 of the coil 2 and the IF of the sub magnetic pole IB.
They are the circumferential width of i and the radial width w2 of the sub magnetic pole IB.

In this embodiment, in order to efficiently obtain the torque corresponding to the torque ripple correction, one pitch width of the sub magnetic pole 1B is associated with the winding width W of the coil 2, and the sub magnetic pole IB is arranged at the outermost circumference of the magnet so as to be as large as possible. At the same time, five correction sub-magnetic poles were provided for each main magnetic pole to obtain fifth-order harmonic torque, which is the lowest order necessary for torque ripple correction.

Further, the radial width w2 of the sub magnetic pole IB is set to be 1/3 or less of the radial width W of the main magnetic pole to minimize the reduction in the area occupied by the main magnetic pole IA. Therefore, according to this embodiment, effective torque ripple correction can be performed and torque reduction can be kept to a minimum.

FIG. 7 is a partial plan view showing another embodiment of the magnet according to the present invention. In this embodiment, among the five correction sub-magnetic poles, the center and both end correction sub-poles are the same as in the example shown in FIG. 1, but the two in the middle are non-magnetized portions IB'. .

FIG. 8 shows a slightly different embodiment of the present invention, in which of the five sub-poles, three sub-poles at the center and at both ends are magnetized at the same time as the main pole.

In the examples shown in FIGS. 7 and 8 as well, the opening angle and the radial width of the sub-pole portion are the same as those described in connection with FIG. 4. By combining such a magnet with the coil described in FIG. 5, the operation is exactly the same as that described in FIG. 6.

Further, in FIG. 3, a magnet rotation type motor has been explained as an example, but it goes without saying that a coil rotation type brush motor can be constructed using each of the magnets and coils described above.

FIG. 9 is a perspective view of a magnet and a coil in a case where a brushless motor is constructed by using the magnet and the coil as circumferentially opposed types. As shown in the figure (^), five sub magnetic poles 11B are provided at the outermost part of the cylindrical magnet 11 for each of the main magnetic poles 11A. The relationship between the arrangement of the sub magnetic poles is the same as that of the surface facing type magnet described above. The circumferential dimension of each sub-pole is each main lI! The circumferential length of one pole is approximately 115. The lengthwise dimension is 173 or less of the lengthwise dimension of the main pole. In such a cylindrical magnet, there are six coils 1 shown in the same figure (B).
2 can be stored. The central angle of each coil 12 is approximately equal to the central angle of each main magnetic pole, and the winding width of each coil 12 is approximately equal to the central angle of each main magnetic pole.
The circumferential dimension of B should be the same or smaller.

The circumferentially opposed brushless motor configured in this manner can also effectively correct torque ripples in the same manner as described with reference to FIG.

In both surface facing type and circumferential facing type brushless motors, the number of main magnetic poles is not limited to the 8 poles illustrated, but may include 4Fi,
Needless to say, it can be applied to 5 poles, 10 poles, 12 poles, and other numbers of poles.

[Effects of the Invention] As explained above, according to the present invention, five sub magnetic poles are provided for each main magnetic pole part, so even if the area of the sub magnetic pole part is small, the fifth order for torque ripple correction is Harmonic torque can be obtained efficiently, and the reduction in torque generated by the motor can be kept to an extremely small level.

Specifically, when the torque ripple was suppressed to a few percent or less, the motor starting torque could be reduced by 5 to 10%. This is a big improvement over the conventional system, in which starting torque was sacrificed by 20 to 40% in order to suppress torque ripple to a few percent or less.

As described above, the present invention makes it possible to achieve both the contradictory sacrifices of suppressing ripple and preventing a decrease in starting torque.

[Brief explanation of drawings]

Fig. 1 is a plan view of an example of a multi-pole magnet according to an embodiment of the present invention, Fig. 2 is a plan view of a yoke to which an air-core coil is fixed, and Fig. 3 is a sectional view of an embodiment of a three-phase brushless motor of the present invention. Fig. 4 is a partial plan view of the magnet, Fig. 5 is a plan view of one air-core coil, Fig. 6 is a detailed explanation of the present invention, and Figs. FIG. 9 is a perspective view of a circumferentially opposed magnet and a coil, and FIGS. 10 and 11 are plan views of conventional magnets, respectively. 1...Magnet, 18...Main magnetic pole, 1B...Sub magnetic pole. 2... Coil, 3... Rotor yoke, 4... Stator yoke, 5... Rotor shaft, 6... Bearing, 11... Magnet, 118... Main magnetic pole, 11B... Sub-magnetic pole, 12...coil. Fig. 1 Fig. 2 Coil Fig. 2 Fig. 4 Fig. υ Fig. 6 Fig. 8 Fig. 9

Claims (1)

[Claims] 1) A three-phase brushless motor having a multi-pole magnetized magnet and a plurality of air-core coils facing the magnet, wherein the magnet has an even number of main magnetic poles, each of which has an even number of main magnetic poles. The main magnetic pole has a sub-magnetic pole part on the outermost part of the surface facing the coil, and the sub-magnetic pole part is made up of five sub-poles of substantially the same shape that divide the outermost part of each of the main magnetic poles into five parts, The three-phase brushless, wherein the opening angle of the coil is approximately equal to the opening angle of each main magnetic pole of the magnet, and the winding width of the coil is approximately equal to or less than the circumferential width of each sub-pole. motor. 2) The three-phase brushless motor according to claim 1, wherein the magnet and the plurality of air-core coils face each other, and the magnet has a disk shape. 3) The sub magnetic pole part is characterized in that adjacent sub magnetic poles are opposite magnetic poles over the entire circumference, and the sub magnetic pole located at the center of each pole of the main magnetic pole part has the same polarity as the main magnetic pole part. A three-phase brushless motor according to claim 2. 4) The polarity of the sub magnetic pole located at the center of each pole of the main magnetic pole section is the same as the polarity of the main magnetic pole section, and the two adjacent sub magnetic poles are substantially non-magnetized. A three-phase brushless motor according to claim 2. 5) The second aspect of the present invention is characterized in that the radial width of the sub magnetic pole portion is 1/3 or less of the radial width of the main magnetic pole.
3-phase brushless motor described in section. 6) The three-phase brushless motor according to claim 1, wherein the magnet is a cylindrical magnet, and the plurality of coils are housed within the cylindrical magnet and face the magnet. .